I need help with removing Allen head bolts that have partially dissolved!! The bolts fasten the flywheel to the crankshaft on my 1977 300D and two bolts are missing part of one side. The proper size Allen head wrench spins freely in the head and the next size up Allen wrench is too large.

I plan on drilling the head of the bolts off and back out the remainder with a pair of pliers (hopefully) and, if needed, drill the remaining portion to fit an easy out tool and then back out the rest.

Does anyone have any experience with this problem or suggestions about another way to remove the bolts?

My main concerns are the hardness of the bolts and the size of the shank (these are the waisted shank type bolt that stretch when torqued and have a smaller diameter than the threaded portion).

I have a thread about this problem in the Tech Forum that goes into a bit more detail. If anyone has a comment or suggestion, then please read that thread and let me know your thoughts.

Thanks,
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

you could JB weld a Allen Head wrench to it (never done it, got the idea from the back of the JB Weld box)

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/119226-1982-300d-sale.html#post852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

if they prove too hard to drill,you can always grind the heads off with a die grinder and rhe right size grinding point and then soak them and back them out with vice grips.......
William Rogers.......

"JB weld an allen head wrench to it". I think Capt Kirk is out in space again. JB is good but not that good.


Try welding another bolt to the broken allen screw. Try removing the broken allen screw quickly, because the heat may loosen it.


P E H

.......

JB weld is pretty darn good. But like I said, I've never done it, I got the idea off the back of said JB Weld.

The only time I had a problem removing Flywheel bolts was on my old VW. The Fly Wheel sheered off the bolts after I had overtightened them. I got the remains out with Vice Grips.

__________________
2005 Audi A4 1.8T CVT -Silver/Black "Siegfried"

1982 300D - Silver/Blue "Ralph" -For Sale:
http://www.peachparts.com/shopforum/showthread.php?p=852260

1989 VW Diesel Jetta Blue/Blue "Bodo" RIP

Hey Guys!

Thanks for the input and suggestions. After reading your replies and those from my post in the Tech Forum I began by inspecting the other bolts and found several others that looked like the inner hex part was slightly rounded. I used my Snap-On 8mm Allen head hex key that is in a socket (almost new and in like condition) and tapped it with a plastic mallet into the questionable bolts to fully seat the hex key into the head. Five of the bolts rounded off, meaning I had 7 out of 12 flywheel mounting bolts that were going to require special procedures to remove.

I decided to drill the heads to relieve the torque/stress on them. Seems M-B planned on this procedure because there is a small hole in the middle of the hex head that extends to just beyond where the shank changes to the bolt head. I started with drilling the small hole to a size just larger than it's OD - making sure that I was making a trued hole aligned with the center line of the bolt - rather the best I could since I was doing this by hand and sitting on the floor. Then I used progressively larger drill bits until I drilled out the hex head portion completely with a 23/64" bit, but no deeper than the hole M-B originally had in the bolt. I used a bit of oil as I drilled, cleaned out the shavings as needed, and sharpened the bits when needed. Then I used a small chisel & hammer to cut a small notch in the head of the bolt, then I placed the chisel in the notch facing in the direction of loosening the bolt and hit the chisel with a hammer to loosen the bolt (kind of like a socket and ratchet, but using a chisel as the socket and hammer as the ratchet - I've done this lots of times in the dim, dark past with lots of success). I was able to back out all but 2 of the bolts this way.

The last two bolts I drilled out with a 3/8" drill bit (next size up from the 23/64" drill bit), then I used the chisel and hammer to break the head off (not too much effort), the heads broke off cleanly because only a very thin amount of metal was left (the centering of my drilling was very good - surprising since it has been a long time since the last time I had to do something like this, and the engine was on the floor which is not the best place to try and line up precise drill holes despite the small hole already in the middle of the bolt). Then I removed the flywheel (after making small punch holes to show alignment with TDC of #1 piston and the timing marks on the front balancer). Vise grips on the remaining shanks did not work initially. I looked more closely at the threads and saw some material that looked like thread lock compound. Put a bit of penetrating oil on the thread and let them soak for a few minutes, then took a center punch and hit a good blow on the bolt to try and loosen it, and then the vise grips worked fine to remove the bolt. At least I did not have to drill more holes to use an easy out tool to remove the bolts. If drilling did not work, then grinding, welding, epoxy, or whatever else I could do would be tried to remove these bolts.

Most important, the flywheel itself was not touched by my drilling or other procedures - so it is perfect and the balance is not affected - Whew!

I planned on replacing the flywheel bolts anyway since they are the waisted shank type, but I did not envision having to replace them because 7 out of 12 would be totally unusable after I got them out!!

When I tried to connect an adaptor plate to mount the engine onto an engine stand I found the bolts I had were too short (these bolts connect the auto trans to the engine). Off to the bolt/nut/fastener supplier just as a mini rush hour from the medical center began (and where I live close to), the rain began, and the bolt supplier is located on the other side of a major highway improvement project that is 5-6 miles long (we're about half way through a 6-7 year improvement program - which will be out-of-date as soon as it is finished, meanwhile traffic is really bad at times - like a slow moving parking lot).

Tomorrow, the engine goes on the stand and the fun really begins as I TDI (teardown & inspection) for an overhaul.

I'll keep all posted as I progress through the overhaul. This engine has a unique story behind it and I will write about it in a later post. I need to warn fellow 300D diesel owners of potential problems with the head gasket for 300D engines up to the 1978 model year (1979 M-B redesigned the head gasket, changed the head bolts to the 12-point head waisted shank type that is final torqued with a 90 degree turn, and harder head bolt washers).

Till then - Thanks Again!

Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.